Electric power converting apparatus



ELECTRIC POWER CONVERTING APPARATUS Filed 00:, 28. i950 Inventor:(llodius H. Willis,

His Attorney Pet entedckug23,1932

UNITED ta 15;

M in f MyMarianna;aerate pbwiicci lj-g yerting app aratns 1 and more;particularly to a 1 such apparatus 1 including 1 electric valves adaptedto convertdirect current intoalterr a iro i qmt tmimwa menacemama Q QB.Q QE l i it m w j at iatioilfmea camber 28,;1930. fsen ar No. 491,807.

aawi gpiantitt p weaned itt e appended a m a The le fi l re ef th accompnying dr w g a'dieei m e representation o fIny invention as applied to aa Refe ing t the s ng e e f h d linea a e s o n anfl pr m s for ece v nn r y fr m the d c urr n c 0 9 vertingitinto alternating current and deyy c livering it to the receiving circuit 11.; This 00 j apparatuscomprises "a SBI'lQSQlI'QllltrlIlChldr ing an; electric valvel2, aninductive winding lBQ ndaH e tr alve ltre n e i e y, 1

nected across the direct current circuit 10 and r 3; natingcurrent.

a stype o i verter:

Heretofore there havebeendevisedvnumefi oust arrangements including?electric valves l I -for converting direct current into alternating jcurrent; When 1 operating at very high fre+ 10 quencies it qhas :beenfoundthat certain f these 3 arrangements utilizing electric valves a 1of the vapor electricfdischarge type will occasionally short circuit thedirect current cirr throughfthe electric valvesmfWhilethis 1 315 shortcircniting of thef direct: current circuit naylbeinfrequentitsconsequences may be ser es circu t. Electnc valves 12,and 14 are provded with an anode a; cathode, and a conserious if allowedtolpersistiforanycons1der- 11: is 'i a further object of my invention :to

providefani oscillating circuit associated with a a a an? apparatusincluding 1 electric .valves for E flconverting directlcurrentintorelativelyihigh l -irequency'lalternating current bygmean's of:which any shortlcircnit throughihe electric valves williheinstantlycleared. r

paratus for converting a direct current 1 into alternating current,which may a be i of any of 31 the several types wellknownin the artsuch,

for example, as i the so called series inverter to which Ihave shownniyinvention applied; :This oscillating circuitcomprises a relativelythroughthe electricvalves of the'inverter; a For 5a better understandinga; of my invenf stionf togetherfwith other {and further objects a;thereof, reference is" bad to theraccomp anying a second series circuit;comprising capacitors g5 15; and 16 connected parallel to the first inwhichthe starting; ofcurrent inthe valves is determinedby thepotentialonthe control grid but j in which the current throughf the v ves may ente p d yi rr uc n the anode potential below its critical value.

transformer -20 and the current limiting resistors 2 1 and 22,respectively The prirnary prefer to use vapor electricpdischarge valvesy {The receiving circuit ll isenergized from the jsecondarywinding of atransformer 17 the p im y W d ng; of wh ch necte betwee Ml e ec riw m pt Qfth flin uctive winding: Band the junction between capacitors15 and16, The control grids of e ec ric valv s 2 1 nd l4: are energized firmthe; secondary windings: l8 and 519 of a grid winding of thegridtransformerQOis connected parallel with the primary winding of thepower rtransiorlner 17. My; improved garrangernent for eliminating shortcircuits in the electric valves Hand 14 comprisesa reactor23; connectedin series with the direct current source 10 and a capacitor 24 connected across the direct current circuit between the} reactor 23 andthepower converting apjparatus The reactor 23 may be the usual smoothingreactor ordinarily connected in s es w ap wer n e n app r u b this typeand,;t0gether with the capacitor "2 t a e lterv i cuit gsuppr ssnyi'alternating current componentin the; current drawn fromthe directcurrent circuit 10. i The operation of the power converting apparatusper se Willfbe well] understood by. those skilled in the art; "Assumefor example V that'the electric valve 12 firstconductscur 7 rent.Current Will'then' flowfronithe positive direct current line 10through'tl e reactor-23,

electric Valve 12, the ugper portio lof iuduce tive windingl8,tliepr1inar W V transformer 17 and will char e the capac tor '16 tosubstantiallythe potential o fthie direct current circuit. As thecurrentflowsthrough v theprimary Winding .offthe transiormer .the,potentialjacross its terminals is applied to" the rimary Winding of a,the grid trans-t forrner 20 and Lthegc onnections of thef'second arywindings l8fandl91are-such that a neg-Q atite potential will beimpressed fuponkthe grid of electricvalre IQandaIpoSitii/e potentialwillbei 'inipre'ssed u'pon'the gridof elec 1,, tricva-lve Mat the-end--oiftlieiirst half-cyclei Bythe tiniie the ca'jpacitor 16 becomessubstam tiallycompletely charged the potentialfof the grid ofelectricvalve 14 will be sufiicientl y positive t'oinake 'valvie llconductiVeLFThe charging current for: the l capacitor" 15 Will now flowfr o'm the positiire directfcurrent' line through the reactor 28; thecapacitor 15; the primaryiwinding of the transformer 17; the lower halfof inductive winding '13 and a electric valve 14 During" thesame-interval Tot time the capacitor 16 will also discharge Winding 13and the electric valve 14.1 133 the through the primary winding: of "thetransformer 17 5 the lower halffof the inductive time the capacitor 15"becomes; substantially I -charged f and the capacitor1-6'-1supstantially V discharged the "grid potential supiiliedto the insecondary windings" l8; and 19 ofjthe grid "transformer will have ijreiiersefd olarity and have reached such-"a niagnitiide asl'to" renderthe electric "Valve 12 conducting and the elec iingtransferredhetweenfelectric talves' '12 land Willbe notedthat duringYsuccesisiveYhalf cycles the currentfiows inlopposite wdirections through the"primary winding of fth e ftransliormer 17 with the result that analternating current at will he -deliirered {to the freceiving circuit11:

'It'is Wellun'derstood 'by lthose skilledfin thelart that thecharacteristics of the vapor :elefctric discharge ValVes l2 and MQaresuch thattheir control gridsare effective to pre- 1 fvent the startingof an are through the Valves; onlyiin-case-the .vaporcontained in the{Valves fiis substantiallydeionized}? After the valve has' heen carryingcurrent, which is subs'es *qu'ently interrupted,a finite tinie isrequired fortlie gases to become deionized andjincase positive potentialis {applied to the anode H of a valve before it becomes 1 completely deionized; the valve Will -conduct current even me ia though its grid isexcited with a'negative pouremia, In case, for example, the electricvalve 141 isrendered conductive at the same,

instant'thecurrentis interrupted in electric I alve 12 or before theValve 12has had time to deionize; 1 a virtual short OlITCIlityfOI theoif oscillation or one valveicircuit may; be

short circuit, will occur as V explained; above.

If such a short circuit doesxoccur; the capaci iductive winding" 13j-andthis oscillatory idistors le -and 16) will discharge throughithe' ind0charge will momentarily interrupt the me rent in electric alveslZ and?13. 1 ,However,

the"; natural period "of 7 {this .Eoscillatory dis charge" is the same"as that of thejindividual Valvevcircuits] and" will eonsequentlyibe lessthan the :deionization period of the electric Valves. "The capacitor 124and athe inductive r windinglfii which form ;a=second oscillatorycircuit, Will immediately discharge through this short circuit and; asthecapacitorfit 1;

oscillates to somefrlegative potential, the cur rent in electricrvalves12 and 14" WilLbe in,

stantllyainterrupted due to the reversal-of the a anode potential. Th'ecapacitor 24: wil1 now Joe recharged from ithejsource throughathereactoriflb j s, The inductanceflflii is very: large comparedtothatoftheinductiVe winding 13 l f with a res'ult thatthe naturalperiod ofitoscil -l f i'lat ion' ot the .jreactor.23 .andjthe capacitor24 is much a greater than that of the. oscillatory :circuitcomprisingthe ic'apacitor 24L and the v v inductiwe windingm and is suflicientlylong that theitiinelrequired to charge the capacitor Ettaa,potentialsuificient to sen dza current through the valves 12 and 14 and theinducs tit e Winding 13 is substantially A greater than tv'ill*restartitslnormalf operation as described above; In someacaseslit mayhe foundidesirw able .toduplicaterthe filter circuitcomprising v 1 the:reactor 23 andicapacitor 24-to :aid in fil-i tering any r alternating:co np onent of current iron the direct current circuit 10 and to. in-

the deionizationfperiod ofthevalives 1'2 and J "14, so that'loy thistimefitheirrespectiwe grids will-have regained controlvandthe apparatus1 crease the gcertainty. of'operationi of the .ajoparatus to interruptshort circuits"; that is,

' a second capacitor m y. lhe' connected .iac ross :theacircuit 1 0behind ithei reactor. :23; l and:v .a

gsecojnd reactor-connected series therewith,

come substantially equal to oreven lessthan 13 theldei onizationvperiod"otitlie rzyalves and a1 i as will be well understoodby those skilled inItheartr While I have I my invention and, I, therefore, aim inltheMappendedclaims to cover all such changes 15 p a a currentcomprlsmganosc llatlngcircuit1na eluding a vapor electrlc valve meansfor clearing a short ClI'Clllt 1 through said valve and;:n1odificationsqasaiall within the true spirit and-scope oimyinvention; i

What I claim as new and desire tosecure by lLetters Patent of the UnitedStates, is:

1;In combination with an apparatus for converting direct current intoalternating comprising a second oscillating circuit also including saidvalve, said second circuit havmg anaturalperi'od of oscillationsubstantially greater than thatof said first circuit.

5. Means for clearing a short circuit in a 1 a p a a a series inverterincluding a direct current described what I at present consider thepreferred embodiment ofmy invention, it will be obvious to those skilledin the art that various changes and modifications may be made withoutdeparting from circuit} and a plurality of :vapor electric valves andan' inductive Winding serially connected across saldcircuit, comprlsmgaf capacitor associatedwith sa1d1nverter,sa1d a capacitor and saidinductivewinding having a natural periodof oscillation substantiallygreater than the deionization time of said valves, and an inductance insaid direct cursubstantially greaterthan that ofsaid capacitor and saidinductive winding.

Inwitness whereof, I have hereunto set my hand this 27th day ofOctober,1930. 1 q

rent circuit, the naturalperiod of oscillation 1 of said inductance andsaid capacitor being a CLODIUS H. WILLIS,

2. In combination with an apparatus for converting direct current intoalternating 1 current comprisingan oscillating circuit ineluding a vaporelectric valve, the natural a period of oscillation being of thesameorder of magnitude as the, deionization period of a i said valve,means for clearing-a short circuit a p through said valve comprising asecond os-g cillating circuit also including said valve a ii having anatural period of oscillation subthe deionization pestantially greaterthan riod ofsaidvalve. a a 3. In combinationwithanapparatus forconverting direct current into alternating current ncludlnga pair, ofvapor electric a valves and an inductive winding serially a a connectedacross saidsource and a capacitor associated therew1th,means for clearng a shortcircuitthrough saidvalves compris ng a a reactor having aninductance large com-v pared to that of said inductive winding,

connected in series in said direct current circuit, a second capacitorconnected acrosssaid circult between Sald reactor and said appaa"ratusand hav ng a capac tance greater than said first ca acitor; i

4. In com ination with an apparatus for converting direct current intoalternating a current comprising a direct current;c1rcu1t,-

a ser es ClI'CIllb includln a Vap 01leCt1f1Q valve, an inductive win'ng, anda second electric valve respectively, connected acrossthejdirect current circuit, a pairof capacitors seriallyconnectedlacross said} circuit,

and a load circuit connectedbetween the electrical midpoint ofsaidinductive wind-1 ingand the connection between said cae0 pacitors, meansfor clearing a short circuit through said valvesand said inductivewindting comprising; an inductance serially con- ,nected in said directcurrent circuit, and a 3 capacitor connected across sald circuit betweensaid inductance and said apparatus.

